The · Ø ·Ô and ·Ò relative wavefunctions and their asymptotic normalizations are considered in the framework of the generator coordinate method (GCM) and compared with ATMS (amalgamation of two-body correlation into multiple scattering processes) method which used the realistic Reid soft core interaction. The asymptotic normalization of relative wavefunctions provide various coupling constants, the cluster probability amplitude (the so-called ½ ¾ -factor) and matter RMS radii. These wavefunctions are also used to obtain À , À Ø Ô and À Ò vertex functions in the virtual decay of He. The extrapolation of vertex functions for negative values of Õ ¾ upto the corresponding poles provide the vertex constants which are comparable with other estimates. It is noticed that in GCM the coupling constants ¾ for À vertex is less than 2 as has been obtained in the forward dispersion relation technique.